1. Field of the Invention
The invention relates generally to the field of photography, and in particular to a film cassette containing a film spool about which a filmstrip is coiled. More specifically, the invention relates to a film cassette having a spool lock for preventing rotation of the film spool and a light-shielding door that can be opened to permit film movement out of and back into the cassette interior.
2. Description of the Prior Art
U.S. Pat. No. 5,115,268 issued May 19, 1992 discloses a film cassette comprising a light-trapping plush for preventing ambient light from entering the cassette interior through a film egress/ingress passageway, a film spool supported for rotation in film unwinding and film winding directions, and a locking pawl supported for movement into engagement with the spool to secure the spool and out of engagement with the spool to release the spool. The spool has a coaxial ratchet wheel with assymmetrically shaped teeth. The locking pawl appears to be a rigid beam member which is pivotally mounted at one end and has an assymmetrically shaped detent portion at an opposite end. A curved spring arm portion of the locking pawl extends from the end of the rigid beam member that has the detent portion, to bias the detent portion to between any two adjacent ones of the teeth in order to secure the spool. To remove the detent portion from between the two adjacent teeth, an engagement release portion of the locking pawl is turned to pivot the rigid beam member against the contrary urging of the spring arm portion. The engagement release portion then is held in the turned-to position to maintain the detent portion separated from the ratchet wheel. When the engagement release portion is released, the spring arm portion is free to pivot the rigid beam member to return the detent portion to between any two adjacent ones of the teeth in order to re-secure the spool.